Skid landing gear with rollers

Abstract

The present invention relates to a landing gear (1) equipped with at least two first wheels (36, 37) mounted on two respective first free wheels (51, 52) connected to a first skid (11) and configured during a landing phase to lock in the direction of elastic return during a movement of the first skid (11) in a first direction (401) from the first skid (11) to a second skid (12) and to be free in the direction of penetration during a movement in a second direction (402), at least two second wheels (41, 42) being mounted on two respective second free wheels (53, 54) connected to a second skid (12) and configured during a landing phase to lock during a movement of the second skid (12) in the second direction (402) and to be free during a movement in the first direction (401).

Description

[0001] The present invention relates to a skid and roller landing gear, the landing gear being intended for an aircraft such as an aircraft having a rotary wing for example. In particular, the aircraft may be a drone capable of landing on the deck of a ship.

[0002] Conventionally, a rotorcraft has a landing gear on which the rotorcraft rests on the ground. Among the landing gears, a skid landing gear is equipped with a first skid and a second skid intended to be in contact with the ground. The first skid and the second skid are transversely spaced from each other, being located on either side of a longitudinal - vertical plane of symmetry of the landing gear, or even of the rotorcraft.

[0003] In addition, the skid landing gear is usually provided with a first cross member and a second cross member to connect each skid to a structure of a rotorcraft.

[0004] Each sleeper comprises a first leg connected to the first pad and the structure, and a second leg connected to the second pad and the structure. Each sleeper may be discontinuous, or continuous by comprising a central section connecting the first leg to the second leg.

[0005] The first crossmember may be referred to as a "rear crossmember" since this first crossmember is connected to the rear portions of the first and second pads. Conversely, the second crossmember may be referred to as a "front crossmember" since this second crossmember is connected to the front portions of the first and second pads.

[0006] Furthermore, the first skid is provided with a first longitudinal support portion, the second skid being provided with a second longitudinal support portion. The first longitudinal support portion and the second longitudinal support portion jointly define a contact plane of the landing gear on the ground when the aircraft is placed on flat ground. Such a contact plane is hereinafter referred to as a “lift plane”.

[0007] In addition, the landing gear may comprise a first front portion extending longitudinally and in elevation from the first longitudinal support portion. Similarly, the landing gear may comprise a second front portion extending longitudinally and in elevation from the second longitudinal support portion. The first and second front portions may be made from a single piece and may have the same characteristics as the respective first and second longitudinal support portions. The first and second front portions may be part of a front crossmember.

[0008] Documents US 2641423 and FR 2749561 describe skid landing gear.

[0009] Document FR 3 014 079 A1 presents a skid landing gear equipped with at least one balance beam.

[0010] Document FR 2 995 874 presents a skid landing gear fitted with a stiffener.

[0011] Document EP 2 641 831 presents a pad secured to two branches of oscillating crosspieces.

[0012] Furthermore, an aircraft equipped with skid landing gear may sometimes experience a rebound phenomenon during a landing phase. During such a landing phase, the landing gear may store energy by deforming. Some of the energy stored by the landing gear may be released when the load factor experienced decreases. This may result in the aircraft bouncing.

[0013] In another aspect, the materials of the skid landing gear components that are to be in contact with the ground may be chosen to have relatively low coefficients of friction. Thus, these components do not artificially increase the load factors experienced during a landing. On the other hand, the landing gear may be liable to slip in certain extreme conditions, such as on the deck of a boat and in the presence of large waves. The aircraft may then include anchoring systems.

[0014] However, manually moving an aircraft equipped with skid-mounted landing gear can be tricky on the ground due to the friction of the skids on the ground. Specialized tools can be used to move an aircraft stationary on the ground, such as trolleys or handling wheels, for example.

[0015] Documents CN 216 636 810 U, JP H10 129597 A, US 11 230 372 B1, US 2641 423 A, and EP 2 944 567 A1 show skid landing gears with wheels.

[0016] The present invention then aims to propose an innovative landing gear making it possible in particular to combat the rebound phenomenon. Such an innovative landing gear may tend to have optimized stability following a landing, and / or to be more easily handled by an operator on the ground compared to a conventional skid landing gear, and / or to limit the wear of the skids compared to the wear of a conventional skid landing gear, and / or may tend to participate more effectively in avoiding a ground resonance phenomenon.

[0017] The invention thus relates to a landing gear provided with a first skid and a second skid.

[0018] The landing gear comprises at least two first ground contact rollers mounted on two respective first free wheels which are connected to the first skid, each first free wheel being configured to lock during an elastic return phase during a movement of the first skid in a first direction and to be free during a sinking phase during a movement in a second direction opposite to the first direction, the first direction going from the first skid towards the second skid, the landing gear comprising at least two second ground contact rollers mounted on two respective second free wheels which are connected to the second skid, each second free wheel being configured to lock during the elastic return phase during a movement of the second skid in the second direction and to be free during the sinking phase during a movement of the second skid in the first direction.

[0019] The term "ground contact" means that the associated wheels are in contact with the ground when the landing gear is resting on the ground. Thus, a low point of each wheel may be located in a lift plane defined by longitudinal support portions of the first and second skids, or even below this lift plane in flight.

[0020] The expressions "each first freewheel being configured to lock during an elastic return phase during a movement of the first pad in a first direction and to be free during a depression phase during a movement in a second direction opposite to the first direction, the first direction going from the first pad towards the second pad," and "each second freewheel being configured to lock during the elastic return phase during a movement of the second pad in the second direction and to be free during the depression phase during a movement of the second pad in the first direction" mean that each freewheel allows the associated caster to rotate naturally on itself in a single direction of rotation, and blocks the caster when this caster tends to perform an inherent rotation in a direction opposite to said single direction of rotation.

[0021] The term "on itself" refers to a proper rotation of the caster around its freewheel and an associated axis of rotation, this axis of rotation being a central axis of the associated freewheel. The term "rotation" subsequently always refers to the proper rotation of a caster.

[0022] The expression "nutation angle" subsequently designates the angle separating the axis of rotation of a caster and a plane, this plane passing through the longitudinal axis of extension of the corresponding longitudinal support part and being orthogonal to the support plane of the landing gear. The term "pivoting" used for certain variants subsequently refers to a pivoting of the freewheel / caster / axis of rotation assembly relative to the corresponding skid around a pivoting axis, a pivoting inducing a variation of the nutation angle.

[0023] According to a convention and in the remainder of the description, this nutation angle can be counted positively in the clockwise direction seen from above and on the ground for the first wheels equipping the first skid. Symmetrically, the nutation angle can be counted positively in the counterclockwise direction seen from above and on the ground for the second wheels equipping the second skid. For example, the first skid can be called the “left skid” and the second skid can be called the “right skid” in the eyes of an observer located at the rear of the landing gear.

[0024] The nutation angle of a caster is thus considered zero when its axis of rotation is parallel to the longitudinal axis of extension of the corresponding longitudinal support part, and equal to 90 degrees when its axis of rotation is in a plane orthogonal to the longitudinal axis of extension of the corresponding longitudinal support part.

[0025] During the first phase of a landing, called the sinking phase for convenience, the track between the first skid and the second skid tends to widen. The first skid and the second skid tend to move away from each other, the crosspieces deforming. Following impact with the ground, the first skid moves in the second direction and the second skid moves in the first direction. The rollers roll on the ground, performing proper rotations around their respective axes of rotation, and do not hinder the movements of the associated skids. The rollers allow the lateral deformation, at least partially elastic, of the landing gear.

[0026] On the other hand, during the second phase of a landing, called the elastic return phase, the landing gear tends to return to its equilibrium shape by restoring the energy accumulated during the previous deformation of the landing gear. The free wheels tend to prevent the wheels from rotating on themselves. Therefore, the wheels, thanks to the coefficient of friction between the wheels of the wheels and the ground, tend to slow down the elastic return of the pads, which tends to reduce a bounce or even prevent the occurrence of a bounce. The return to the equilibrium position of the landing gear can be done gradually, or an operator can intervene to unlock at least one wheel per pad, by disengaging the free wheels or using external tools that will relieve the vertical force exerted on the landing gear.

[0027] Furthermore, depending on the embodiment and as described below, these wheels may possibly facilitate the maneuvering of the landing gear on the ground and / or may participate in maintaining the landing gear in position on slippery ground and for example on the deck of a ship.

[0028] The landing gear may further include one or more of the following features, alone or in combination.

[0029] According to one possibility, the landing gear may comprise a front cross member provided with a first forward descending leg connected to the first skid and a second forward descending leg connected to the second skid, said landing gear comprising a rear cross member provided with a first rear descending leg connected to the first skid and a second rear descending leg connected to the second skid. The cross members may be continuous or discontinuous.

[0030] Therefore, said two first rollers can be positioned respectively in alignment with the first front descending branch and the first rear descending branch, said two second rollers being positioned respectively in alignment with the second front descending branch and the second rear descending branch.

[0031] This arrangement makes it possible to position the wheels as close as possible to the introduction of forces into the crosspieces which deform during a landing phase. This arrangement makes it possible to avoid introducing parasitic bending moments into the skids. In the case of a landing gear of the type of patent FR 2749561, the distributions of moments between the crosspieces and the skids are not modified.

[0032] According to a possibility compatible with the previous one, said at least two first rollers can be housed at least partially in respective first housings of the first skid open towards the ground when the landing gear rests on the ground, said at least two second rollers being housed at least partially in respective second housings of the second skid open towards the ground when the landing gear rests on the ground.

[0033] The casters are thus in contact with the ground while being protected by the corresponding pads.

[0034] According to a possibility compatible with the previous ones, each freewheel of said at least two first freewheels and at least two second freewheels may comprise an inner ring arranged in an outer ring as well as at least one movable member arranged between the inner ring and the outer ring, the inner ring or the outer ring of a freewheel of a corresponding shoe comprising a blocker per movable member to secure the inner ring and the outer ring when the corresponding shoe tends to move towards the other shoe, one of the inner ring and outer ring being secured to the corresponding wheel and the other inner or outer ring not secured to the wheel being connected to a longitudinal support part of the corresponding shoe.

[0035] For example, the outer ring is integral with the corresponding wheel and the inner ring is connected to a longitudinal support part of the corresponding pad.

[0036] For example, a blocker takes the form of a face of the outer ring capable of wedging the moving member between the outer ring and the inner ring to immobilize the caster when the corresponding shoe tends to move towards the other shoe.

[0037] A moving part can take the form of a ball, a roller, a ratchet for example.

[0038] Each ring that is not integral with a wheel is also fixed in rotation around the axis of rotation of the associated wheel on itself. Therefore, this ring can be described as "fixed" and allows the associated wheel to be blocked when the corresponding shoe tends to move closer to the other shoe. The other ring can be described as "mobile" by contrast.

[0039] According to a possibility compatible with the previous ones, said two first rollers can be arranged respectively around two first inner rings of the two first freewheels, the two first inner rings being connected to the first pad, said two second rollers being arranged respectively around two second inner rings of the two second freewheels, the two second inner rings being connected to the second pad.

[0040] According to a possibility compatible with the previous ones and a first realization, at least one or even each wheel can have a fixed nutation angle.

[0041] Thus, at least a first wheel can have a first axis of rotation on itself fixed relative to the first skate.

[0042] The first caster therefore has a substantially fixed position relative to the first shoe, apart from the mounting clearance. Where applicable, the ring of the first freewheel which is not integral with the associated first caster also has a substantially fixed position relative to the first shoe. The first caster thus only has one degree of freedom in rotation around its first axis of rotation relative to the first shoe.

[0043] For example, said first axis of rotation may be parallel to a first longitudinal axis of extension of a first longitudinal support portion of the first pad. The nutation angle is then zero.

[0044] According to another example, said first axis of rotation may have an angle different from 0 and 90 degrees relative to a geometric axis parallel to this first longitudinal axis of extension, in a braking configuration and for example a nutation angle of the order of 45 degrees according to the convention previously described.

[0045] The use of first casters having respective first axes of rotation parallel to the first longitudinal axis of extension can facilitate the deformation of the landing gear on the ground during the sinking phase.

[0046] Conversely, the use of first casters having respective first axes of rotation angularly offset from the first longitudinal axis of extension can facilitate the immobilization of the landing gear on a mobile landing area.

[0047] According to a possibility compatible with the previous ones and the first embodiment, said two first casters can have first axes of rotation on themselves respectively parallel.

[0048] According to a possibility compatible with the previous ones and the first embodiment, at least a second caster can have a second axis of rotation on itself fixed relative to the second skate.

[0049] The second caster therefore has a substantially fixed position relative to the second shoe, apart from the mounting clearance. Where applicable, the ring of the second freewheel which is not integral with the associated second caster also has a substantially fixed position relative to the second shoe. The second caster thus only has one degree of freedom in rotation around its second axis of rotation relative to the second shoe.

[0050] According to a possibility compatible with the previous ones and the first embodiment, said second axis of rotation can be parallel to a second longitudinal axis of extension of a second longitudinal support part of the second pad, or can have an angle different from 0 and 90 degrees relative to a geometric axis parallel to the second longitudinal axis of extension, for example by having a nutation angle of the order of 45 degrees according to the convention previously described.

[0051] The use of second casters having respective second axes of rotation parallel to the second longitudinal axis of extension can facilitate the deformation of the landing gear on the ground during the sinking phase.

[0052] Conversely, the use of second casters having respective second axes of rotation angularly offset from the second longitudinal axis of extension can facilitate the immobilization of the landing gear on a moving landing area.

[0053] According to a possibility compatible with the previous ones and the first embodiment, said two second casters can have second axes of rotation on themselves respective parallel.

[0054] According to an example of the first embodiment, each first and second caster may have an axis of rotation parallel to the longitudinal extension axis of the associated skate. All the castors are substantially pivoted at 0 degrees relative to the corresponding skates by having zero nutation angles with respect to the skates

[0055] According to another example of the first embodiment, said first axis of rotation of a first caster may have an angle different from 0 and 90 degrees relative to a geometric axis parallel to the first longitudinal axis of extension and said second axis of rotation of a second caster may have an angle different from 0 and 90 degrees relative to a geometric axis parallel to the second longitudinal axis of extension, the first axis of rotation not being parallel to the second axis of rotation. For example, the first axes of rotation of the first casters of the first skate may be parallel to each other, the second axes of rotation of the second casters of the second skate being parallel to each other without being parallel to the first axes of rotation.The first rollers may for example be inclined at approximately 45 degrees relative to the first skate in a first direction when viewed from above while the second rollers may for example be inclined at approximately 45 degrees relative to the second skate in a second direction when viewed from above.

[0056] According to a possibility compatible with the previous ones and a second embodiment, at least one or even each caster can have a variable nutation angle while having the ability to pivot relative to the corresponding skate.

[0057] Thus, at least one first freewheel can be carried by a first support in pivot connection with the first pad around a first pivot axis present in a first transverse plane orthogonal to a first longitudinal axis of extension of a first longitudinal support part of the first pad, at least one second freewheel being carried by a second support in pivot connection with the second pad around a second pivot axis present in a second transverse plane orthogonal to a second longitudinal axis of a second longitudinal support part of the second pad. The pivot axes are not coincident with the respective axes of rotation.

[0058] This architecture makes it possible to optimize the orientation of the wheel concerned in relation to the corresponding skate according to the need.

[0059] If necessary, the rings of the free wheels which are not integral with the associated rollers are then pivotable relative to the corresponding pad.

[0060] Optionally, the landing gear may comprise at least one actuator connected to at least one of the first support and second support. Thus, the actuator makes it possible to orient at least one caster relative to the corresponding pivot axis.

[0061] Optionally, all the freewheels may be carried by respective supports pivoting relative to the corresponding pad, each possibly being associated with at least one actuator. Optionally, the same actuator may act on several supports.

[0062] Thus, the rotation axes of the casters can be pivoted during a landing phase, in order to give zero nutation angles to the casters. On the ground, the rotation axes of the casters can be pivoted to generate nutation angles substantially different from 0 and 90 degrees relative to the corresponding skid to immobilize the landing gear, or 90 degrees to allow the aircraft to be moved on its landing gear.

[0063] Optionally, some casters are arranged according to the first embodiment and other casters are arranged according to the second embodiment.

[0064] According to a possibility compatible with the previous ones and whatever the embodiment, at least one of said casters may include a bandage intended to be in contact with the ground, said bandage being made from a material from the elastomer group.

[0065] Such material can increase the coefficient of friction of the caster on the ground to limit the risk of rebound.

[0066] According to a possibility compatible with the previous ones and whatever the realization, at least one of the free wheels can be disengageable.

[0067] The freewheel can then include an existing manually or motorized disengageable system to release the associated wheel to the ground at the end of a landing phase.

[0068] According to a possibility compatible with the previous ones and whatever the realization, at least one freewheel can be equipped with a brake.

[0069] The invention also relates to an aircraft equipped with such landing gear.

[0070] The invention also relates to a method for limiting a rebound of a landing gear during a landing phase with such a landing gear, the landing gear being provided with a first skid and a second skid.

[0071] This method then comprises, during a landing phase, positioning at least two first ground contact rollers mounted on two respective first free wheels connected to the first skid in landing positions preventing movement of the first rollers towards the second skid, and positioning at least two second ground contact rollers mounted on two respective second free wheels connected to the second skid in landing positions preventing movement of the second rollers towards the first skid.

[0072] Optionally, the method may comprise, during a phase following the landing phase, positioning of the at least two first casters and of the at least two second casters either in respective rolling positions allowing the landing gear to roll on the ground or in respective braking positions limiting the sliding of the landing gear on the ground.

[0073] The invention and its advantages will appear in more detail in the context of the description which follows with examples given for illustrative purposes with reference to the appended figures which represent: there figure 1 , a schematic illustration of an aircraft having landing gear according to the invention, the figure 2 , a side view of a non-swivel caster, the figure 3 , a sectional and side view of the roulette wheel of the figure 2 , there figure 4 , a schematic illustration of an example of landing gear according to the invention with non-pivoting wheels, the figure 5 , a schematic illustration of an example of landing gear according to the invention with non-pivoting wheels, the figure 6 , a sectional and side view of a swivel caster, the figure 7 , a partial view showing the roulette wheel of the figure 6 in a position oriented to present substantially a zero nutation angle relative to the corresponding left skate, namely in a landing position, the figure 8 , a partial view showing the roulette wheel of the figure 6 in a position oriented substantially at 45 degrees relative to the corresponding left pad, namely in a braking position, the figure 9 , a partial view showing the roulette wheel of the figure 6 in a position oriented to present substantially a nutation angle of 90 degrees relative to the corresponding left skate, namely in a rolling position, the figure 10 , a schematic illustration of an example of landing gear according to the invention with pivoting wheels, namely in a landing position, the figure 11 , a schematic illustration of the landing gear of the figure 10 in a braking position, the figure 12 a schematic illustration of the landing gear of the figure 10 in a rolling position, the figure 13 , a diagram illustrating an example of vertical accelerations experienced by a state-of-the-art wheelless skid landing gear during a landing phase, the figure 14 , a diagram illustrating a displacement of a reference point of the landing gear of the figure 11 during a landing phase, the figure 15 , a diagram illustrating an example of vertical accelerations undergone by a roller-skating landing gear according to the invention during a landing phase, and the figure 16 , a diagram illustrating a displacement of a reference point of a landing gear of the figure 13 during a landing phase.

[0074] Elements present in several distinct figures are assigned a single reference.

[0075] Three directions X, Y and Z orthogonal to each other are represented on the figures 1 à 10 .

[0076] The first direction X is called longitudinal. The term "longitudinal" refers to any direction parallel to the first direction X.

[0077] The second Y direction is called transverse. The term "transverse" refers to any direction parallel to the second Y direction.

[0078] Finally, the third Z direction is called elevation. The expression "elevation" and the term "vertical" relate to any direction parallel to the third Z direction.

[0079] There figure 1 presents a rotorcraft 100 according to the invention, such as a helicopter for example. This rotorcraft 100 comprises a structure not shown which rests on a landing gear 1. Only the landing gear is illustrated so as not to unnecessarily weigh down the figure.

[0080] This landing gear 1 comprises a first skid 11 and a second skid 12 intended to be in contact with the ground when the rotorcraft 100 rests on a ground 200. The term ground designates a surface on which a landing gear can rest, and can cover a ground as such or even a landing area of ​​a vehicle or a building for example.

[0081] The first skid 11 and the second skid 12 are respectively arranged transversely to the left and to the right of a longitudinal-vertical plane P1 of symmetry of the rotorcraft 100 or even of the landing gear 1. The right and the left are defined relative to an observer 300 who would look forward from the rear of the landing gear 1.

[0082] Each pad 11, 12 is provided with a longitudinal support portion 111, 121. Thus, the first pad 11 is provided with a first longitudinal support portion 111, the second pad 12 being provided with a second longitudinal support portion 121. Each of the first longitudinal support portion 111 and second longitudinal support portion 121 extends longitudinally, in a rear direction AR of a specific longitudinal axis AX1, AX2, from a front end 112, 122 to a rear end 113, 123.

[0083] Thus, the first pad 11 comprises a first longitudinal support portion 111 extending longitudinally along a first longitudinal axis of extension AX1. In particular, the first longitudinal support portion 111 extends in the rear direction AR from a front end called “first front end 112” to a rear end called “first rear end 113”. The first longitudinal support portion 111 may take the form of a hollow tube, for example with a circular section.

[0084] Likewise, the second pad 12 comprises a second longitudinal support portion 121 extending longitudinally along a second longitudinal axis AX2. In particular, the second longitudinal support portion 121 extends in the rear direction AR from a front end called “second front end 122” to a rear end called “second rear end 123”. The second longitudinal support portion 121 may take the form of a hollow tube, for example with a circular section.

[0085] The second longitudinal support part 121 and the first longitudinal support part 111 may be identical and / or arranged symmetrically on either side of the longitudinal-vertical plane P1.

[0086] Furthermore, the first longitudinal support part 111 and the second longitudinal support part 121 can jointly define a support plane P2 on which the landing gear 1 rests on flat ground, namely on horizontal ground in the terrestrial frame of reference.

[0087] Furthermore, each skate 11, 12 may include a member called “front portion 15”.

[0088] Thus, the first pad 11 comprises a front portion 15 called “first front portion 20”. The first front portion 20 extends forward and upward from the first longitudinal support portion 111. Therefore, the first longitudinal support portion 111 is extended forward by the first front portion 20.

[0089] Likewise, the second pad 12 comprises a front portion 15 called the “second front portion 25”. The second front portion 25 extends forward and upward from the second longitudinal support portion 121. Therefore, the second longitudinal support portion 121 is extended forward by the second front portion 25.

[0090] Each front portion 15 can thus project longitudinally towards the front of the corresponding longitudinal support part 111, 121.

[0091] Optionally, the first front portion 20 and the second front portion 25 are identical and / or arranged symmetrically on either side of the longitudinal-vertical plane P1.

[0092] According to another possible characteristic, the first pad 11 and the second pad 12 can be connected transversely to a rear cross member 2. For example, a first rear descending branch 2a and a second rear descending branch 2b of this rear cross member 2 are fixed respectively to the first pad 11 and to the second pad 12 by usual fixing means 3. These fixing means 3 can comprise sleeves for example.

[0093] The rear cross member 2 may be continuous. A rear top portion 2c is then arranged between the first rear descending branch 2a and the second rear descending branch 2b of the rear cross member 2. The rear top portion 2c of the rear cross member 2 may then be fixed to the structure of the rotorcraft 100 via at least one usual fixing means.

[0094] Alternatively, the rear cross member 2 may be discontinuous and then devoid of the rear top portion 2c. Each rear descending branch 2a, 2b is then attached to the structure via at least one usual fixing means.

[0095] The first pad 11 and the second pad 12 may be transversely connected to a front cross member 4. The front cross member 4 has a first front descending branch 4a fixed to the first pad 11 by a standard connecting piece 5, for example of the sleeve type. In addition, the front cross member 4 has a second front descending branch 4b fixed to the second pad 12 by a standard connecting piece 5, for example of the sleeve type.

[0096] The front cross member 4 may be discontinuous or continuous, comprising a front top portion 4c arranged between the first and second front descending branches 4a, 4b or even fixed to the structure of the rotorcraft 100 via at least one usual fixing means.

[0097] The first skid 11, the second skid 12, the front cross member 4 and the rear cross member 2 may each comprise a single tube or several tubes assembled together.

[0098] According to another aspect, the front cross member 4 may be fixed to each pad 11, 12 substantially between the front end of each pad 11, 12 and the rear cross member 2, or may extend between the two aforementioned front portions according to the example illustrated with dotted lines.

[0099] Furthermore, the landing gear 1 comprises a plurality of ground contact wheels 30 carried by the first skid 11 and the second skid 12, and in particular at least one wheel called "first wheel 35" carried by the first skid 11 and at least one wheel called "second wheel 40" carried by the second skid 12. The reference 30 is used to designate any wheel, the references 35, 36, 37, 40, 41, 42 designating particular wheels.

[0100] Each caster 30 may comprise a bandage 31 forming a tread. The bandage 31 may be made of a material from the elastomer group to give the tread a maximized coefficient of friction. The bandage may have a truncated barrel shape to correctly locate the ground force and to limit the resistant pivoting torques if necessary.

[0101] Each wheel 30 is movable in rotation on itself around an axis of rotation.

[0102] According to another characteristic, each caster 30 is mounted on a free wheel 50 connected to a skate 11, 12. The reference 50 designates any free wheel, the references 51, 52, 53, 54 designating particular free wheels 50 if necessary. Each free wheel 50 is configured to allow rotation of the carried caster 30 in only one direction of rotation.

[0103] Thus, the landing gear 1 comprises at least two first rollers 36, 37 mounted on two free wheels called “first free wheels 51, 52” respectively, or even comprises only two first rollers 36, 37. Each first free wheel 51, 52 is then carried by the first skid 11, or even by its first longitudinal support part 111.

[0104] Each first free wheel 51, 52 is then configured to block, during an elastic return phase of a landing phase, the first wheel 36, 37 carried during a movement of the first pad 11 in a first direction 401 going from the first pad 11 to the second pad 12 and, on the contrary, to allow a rotation of the first wheel 36, 37 around its axis of rotation AXROT1, AXROT11 during a movement in a second direction 402 opposite to the first direction 401. During a sinking phase of the landing phase. During a landing, the elastic return phase follows the sinking phase.

[0105] Likewise, the landing gear 1 comprises at least two second rollers 41, 42 mounted on two free wheels called “second free wheels 53, 54”, or even comprises only two second free wheels 53, 54. Each second free wheel 53, 54 is then carried by the second skid 12, or even by its second longitudinal support part 121.

[0106] Each second free wheel 53, 54 is then configured to block the second wheel 41, 42 carried during the elastic return phase during a movement of the second pad 12 in the second direction 402 and to, on the contrary, allow rotation of the second wheel 41, 42 during the depression phase around its axis of rotation AXROT2, AXROT21 during a movement in the first direction 401.

[0107] During the sinking phase of a landing phase, the first skid 11 may tend to move away from the second skid 12 in the second direction 402, the second skid 12 tending to move away from the first skid 11 in the first direction 401. The crosspieces 2, 4 deform by storing energy, the rollers 30 rolling on the ground 200. At the end of this movement, during the elastic return phase, the free wheels 50 tend to brake, or even prevent the return of the first skid 11 and the second skid 12 towards each other in an equilibrium position by blocking the rollers 30.

[0108] Optionally, the first two rollers 36, 37 are positioned respectively in alignment with the first front descending branch 4a and the first rear descending branch 2a, at their junctions 5, 3 with the first skate 11.

[0109] Optionally, the two second rollers 41, 42 are positioned respectively in alignment with the second front descending branch 4b and the second rear descending branch 2b, at their junctions 5, 3 with the second pad 12.

[0110] According to another characteristic, a caster 30 can be housed in a housing of a skate 11, 12, or even of its longitudinal support part 111, 121.

[0111] Therefore, the first two rollers 36, 37 can be housed at least partially in two respective first housings 114, 115 of the first skid 11. Each first housing 114, 115 is open towards the ground 200 when the landing gear 1 rests on the ground 200.

[0112] Optionally, the two second rollers 41, 42 can be housed at least partially in two respective second housings 124, 125 of the second skid 12. Each second housing 124, 125 is open towards the ground 200 when the landing gear 1 rests on the ground 200.

[0113] There figure 2 shows a view of a roulette 30 carried by a skate 11,12.

[0114] There figure 3 presents a sectional side view of the figure 2 and illustrates an example of a particular arrangement of a caster 30. The caster 30 may be one of the first castors 36, 37, or one of the second castors 41, 42.

[0115] Whatever the embodiment, the freewheel 50 and the caster 30, a freewheel 50 may comprise an inner ring 55 arranged in an outer ring 56.

[0116] The inner ring 35 extends along the axis of rotation AXROT1, AXROT11, AXROT2, AXROT21 of the supported roller 36, 37, 41, 42, this axis of rotation AXROT1, AXROT11, AXROT2, AXROT21 being able to be an axis of symmetry of the inner ring 55.

[0117] One of the inner 55 and outer 56 rings can be described as a “fixed ring”, i.e. substantially immobile relative to the associated axis of rotation, while the other ring is called a “moving ring” by contrast. The moving ring is then integral with the associated caster, the fixed ring being connected to the corresponding pad by a fixed or pivoting support depending on the embodiment.

[0118] According to the illustrated examples, the inner ring 55 may be the fixed ring. Furthermore, the inner ring 55 is attached to the associated pad 11, 12 by a support. Furthermore, the outer ring 56 is then the movable ring made integral with the roller 30 in the usual manner.

[0119] The reverse is possible, the outer ring being connected to the corresponding pad by a fixed or pivoting support, the inner ring being integral with the associated wheel.

[0120] In addition and independently of the nature of the movable and fixed rings, the freewheel 50 comprises at least one movable member 57 cooperating with a blocker 58. The movable member 57 is arranged between the inner ring 55 and the outer ring 56, the inner ring 55 or the outer ring 56 comprising a blocker 58 per movable member 57. The blocker 58 and the movable member 57 secure, in rotation about the associated axis of rotation, the inner ring 56 and the outer ring 57 when the corresponding shoe 11, 12 tends to move towards the other shoe. The inner ring 55 being fixed, according to the examples given, relative to the associated axis of rotation, the caster 30 cannot then rotate about this axis of rotation.

[0121] According to the example illustrated, a movable member 57 takes the form of a roller arranged between two bearings 59, the blocker 58 taking the form of an internal face of the outer ring 56 capable of wedging the roller between it and the inner ring 55 depending on the direction of movement of the associated shoe 11, 12. Alternatively, any type of freewheel is possible, the freewheel 50 being able for example to be a ratchet freewheel.

[0122] According to one possibility, a freewheel 50 can also be disengageable, manually or motorized. Such a freewheel 50 can comprise a motor setting the inner ring 55 in motion, a movable cage carrying the rollers, etc. Reference will be made to the literature for examples of disengageable freewheels.

[0123] Under these conditions, the two first rollers 36, 37 are, according to the illustrated examples, arranged respectively around two first inner rings 55 of the two first freewheels 51, 52 so as to be movable in rotation around two respective axes of rotation AXROT1, AXROT11, the two first inner rings 55 being connected to the first pad 11. The two second rollers 41, 42 are arranged respectively around two second inner rings 55 of the two second freewheels 53, 54 so as to be movable in rotation around two respective axes of rotation AXROT2, AXROT21, the two second inner rings 55 being connected to the second pad 12.

[0124] According to another characteristic and a first embodiment, the fixed ring of a freewheel 50, namely the inner ring 55 according to the example given, can be attached to the associated pad 11, 12 by a support fixed relative to this pad 11, 12. For example, the support then comprises an inverted U-shaped yoke carrying the inner ring 55 and attached to a longitudinal support part 111, 121.

[0125] Thus, at least one first caster 36, 37, or even each first caster 50 may have a first axis of rotation AXROT1, AXROT11 on itself fixed relative to the first pad 11. At least one second caster 41, 42, or even each second caster may have a second axis of rotation AXROT2, AXROT21 on itself fixed relative to the second pad 12.

[0126] The two first rollers 36, 37 may have first axes of rotation AXROT1, AXROT11 on themselves respectively parallel and / or the two second rollers 41, 42 have second axes of rotation AXROT2, AXROT21 on themselves respectively parallel.

[0127] THE figures 4 et 5 illustrate examples of wheeled landing gear having fixed yokes according to the first embodiment.

[0128] According to the figure 4 , at least one caster 50 may have an axis of rotation parallel to the longitudinal extension axis AX1, AX2 of the corresponding longitudinal support part 111, 121.

[0129] For example, each first caster 36, 37 has a respective first axis of rotation AXROT1, AXROT11 parallel to the first longitudinal extension axis AX1. The first castors 36, 37 each have a zero nutation angle, and consequently an orientation at 0 degrees relative to the longitudinal extension axis AX1 of the first longitudinal support part 111, and therefore relative to the first pad 11.

[0130] For example, each second caster 41, 42 has a respective second axis of rotation AXROT2, AXROT21 parallel to the second longitudinal extension axis AX2. The second castors each have a zero nutation angle, and consequently an orientation at 0 degrees relative to the longitudinal extension axis AX2 of the second longitudinal support part 121, and therefore relative to the second pad 12.

[0131] According to the figure 5 , at least one caster 50 may have an axis of rotation which has an acute angle of between 0 and 90 degrees, and for example of the order of 45 degrees plus or minus 10%, relative to a geometric axis parallel to the longitudinal axis of extension AX1, AX2 of the corresponding longitudinal support part 111, 121.

[0132] For example, each first caster 36, 37 has a first axis of rotation AXROT1, AXROT11 which has an acute nutation angle of between 0 and 90 degrees, not included, relative to the first longitudinal extension axis AX1. The first castors 36, 37 have, for example, a nutation angle of substantially 45 degrees relative to the first pad 11 according to the figure 5 and the convention previously described.

[0133] For example, each second caster 41, 42 has a second axis of rotation AXROT2, AXROT21 which has a nutation angle of between 0 and 90 degrees, not included, relative to the second longitudinal extension axis AX2. The second castors 41, 42 have, for example, a nutation angle of 45 degrees relative to the second pad 12 according to the figure 5 and the convention previously described.

[0134] Possibly, no first axis of rotation AXROT1, AXROT11 is parallel, or even orthogonal, to a second axis of rotation AXROT2, AXROT21.

[0135] According to the realization of the figure 6 illustrating a second embodiment, the fixed ring of a freewheel 50, namely the inner ring 55 according to the example given, can be attached to the associated pad 11,12 by a support 60 pivoting relative to this pad 11,12. The figure 6 can represent any 50 freewheel.

[0136] Thus, at least one first caster 36, 37, or even each first caster 36, 37, may have a first axis of rotation AXROT1, AXROT11 on itself pivoting relative to the first pad 11. At least one second caster 41, 42, or even each second caster 41, 42, may have a second axis of rotation AXROT2, AXROT21 on itself pivoting relative to the first pad 11.

[0137] For example, the support 60 of a freewheel 50 may comprise an inverted U-shaped yoke provided with two branches 61, 62 connected by a wall 63, the two branches 61, 62 carrying the inner ring 55 of the freewheel 50. The wall 63 is then in pivot connection with the associated pad 11, 12 in order to be able to pivot around a pivot axis AXP, via a bearing 64 for example.

[0138] In addition, an actuator 80 may be articulated on the one hand to the pad 11, 12 or to a cross member 2, 4 and on the other hand to the support 60, for example to a lever 65 of the support 60. The actuator 80 may be a manual, hydraulic, electric or pneumatic actuator. The actuator 80 may include an integrated control, or may be linked by a wired or wireless connection to a control to be extended or retracted on request. Thus, an operator can maneuver the control to rotate the relevant caster 50 around a pivot axis AXP.

[0139] According to the figure 7 , the actuator 80 can act on the support 60 to place the caster 30 in a landing configuration, the nutation angle of the caster then being zero. The rotation axis AXROT of the freewheel 50 is then in a plane parallel to the longitudinal extension axis AX1, AX2 of the associated pad 11, 12.

[0140] According to the figure 8 , the actuator 80 can act on the support 60 to place the caster 30 in a braking configuration as described previously, the nutation angle NUT of the caster then being equal to 45 degrees according to the example illustrated.

[0141] According to the figure 9 , the actuator 80 can act on the support 60 to place the caster 30 in a rolling configuration. The nutation angle NUT of the caster is then equal to 90 degrees. The axis of rotation AXROT of the freewheel 50 is then perpendicular to the longitudinal extension axis AX1, AX2 of the associated pad 11, 12.

[0142] There figure 10 illustrates an example of a landing gear with pivoting wheels according to the second embodiment. At least one wheel 50 may have an axis of rotation pivoting relative to the longitudinal extension axis AX1, AX2 of the corresponding longitudinal support portion 111, 121.

[0143] For example, at least one first freewheel 50, or even each first freewheel 51, 52, is carried by a first support 69 in pivot connection with the first pad 11 around a first pivot axis AXP1, AXP2, each first pivot axis AXP1, AXP2 being present in a first transverse plane P3, P4 orthogonal to the first longitudinal extension axis AX1.

[0144] At least one second freewheel 50, or even each second freewheel 53, 54, is carried by a second support 70 in pivot connection with the second pad 12 around a second pivot axis AXP3, AXP4 present in a second transverse plane P5, P6 orthogonal to the second longitudinal extension axis AX2.

[0145] At least one first support 69 can further be connected to a first actuator 81, at least one second support 70 can be connected to a second actuator 82. Each support 69,70 can be connected to its own actuator 80, or an actuator 80 can be connected to several supports 69,70.

[0146] There figure 10 shows the landing gear in a landing position with casters having zero nutation angles.

[0147] There figure 11 shows the landing gear in a braking position with first rollers 35 having nutation angles of 45 degrees relative to the first longitudinal support portion 111, and second rollers 40 having nutation angles of 45 degrees relative to the second longitudinal support portion 121 according to the convention previously described.

[0148] There figure 12 shows the landing gear in a taxiing position with casters having nutation angles of 90 degrees.

[0149] THE figures 13 à 16 illustrate the operation of the invention.

[0150] There figure 13 presents a diagram including the time on the abscissa and the vertical acceleration undergone by an aircraft equipped with skid landing gear according to the state of the art during a landing phase on the ordinate.

[0151] There figure 14 presents a diagram showing the displacement of the aircraft's center of gravity during this landing. The diagram illustrates the presence of two bounces after 0.5 seconds and 1 second.

[0152] The method of the invention provides for positioning at least two first casters 36, 37 in landing positions preventing movement of the first casters 36, 37 towards the second skid 12, and positioning of at least two second casters in landing positions preventing movement of the second casters 41, 42 towards the first skid 11.

[0153] There figure 15 presents a diagram including on the abscissa the time and on the ordinate the vertical acceleration undergone by an aircraft equipped with a landing gear 1 with skids according to the invention under the same conditions as for the figure 11 . There figure 16 presents a diagram showing the displacement of the aircraft's center of gravity during this landing. The wheels 30 then make it possible to avoid the creation of rebound.

[0154] Optionally, during a phase following the landing phase and in the presence of mobile casters 30, the method may provide for positioning of the at least two first casters 36, 37 and of the at least two second casters 41, 42 either in respective rolling positions allowing movement of the landing gear 1 on a ground 200 by rolling to reach a configuration of the type of the figure 9 or either in respective braking positions prohibiting lateral and longitudinal movement of the landing gear 1 on ground 200 by rolling, for example of the type of the figure 8 .

[0155] Naturally, the present invention is subject to numerous variations in its implementation. Although several embodiments have been described, it is understood that it is not conceivable to exhaustively identify all possible embodiments. It is of course possible to replace a means described by an equivalent means without departing from the scope of the present invention and the claims

[0156] For example, the same landing gear may comprise rollers 30 of different types, for example at least one fixed roller 30 having an inclination of 0 degrees relative to the associated skid 11, 12 according to the figure 4 , and / or at least one fixed caster 30 having an inclination of 45 degrees relative to the associated skate 11,12 according to the figure 5 , and / or at least one swivel castor 30 according to the figure 6 .

Claims

1. Landing gear (1) provided with a first skid (11) and a second skid (12), the landing gear (1) comprising at least two first ground-contact rollers (36, 37) mounted on two respective first free-wheels (51, 52) that are connected to the first skid (11), each first free-wheel (51, 52) being configured to lock during an elastic return phase when the first skid (11) moves in a first direction (401) and to be free during a sink phase when the first skid moves in a second direction (402) opposite to the first direction (401), the first direction extending from the first skid (11) towards the second skid (12), the landing gear (1) comprising at least two second ground-contact rollers (41, 42) mounted on two respective second free-wheels (53, 54) that are connected to the second skid (12), each second free-wheel (53, 54) being configured to lock during the elastic return phase when the second skid (12) moves in the second direction (402) and to be free during the sink phase when the second skid moves in the first direction (401).

2. Landing gear according to claim 1, characterised in that said landing gear (1) comprising a front cross-member (4) provided with a first front descending branch (4a) connected to the first skid (11) and a second front descending branch (4b) connected to the second skid (12), said landing gear (1) comprising a rear cross-member (2) provided with a first rear descending branch (2a) connected to the first skid (11) and a second rear descending branch (2b) connected to the second skid (12), said two first rollers (36, 37) are positioned respectively in line with the first front descending branch (4a) and the first rear descending branch (2a), said two second rollers (41, 42) being positioned respectively in line with the second front descending branch (4b) and the second rear descending branch (2b).

3. Landing gear according to any one of claims 1 to 2, characterised in that said at least two first rollers (36, 37) are housed at least partially in respective first housings (114, 115) of the first skid (11) that are open towards the ground (200) when the landing gear (1) is resting on the ground (200), said at least two second rollers (41, 42) being housed at least partially in respective second housings (124, 125) of the second skid (12) that are open towards the ground (200) when the landing gear (1) is resting on the ground (200).

4. Landing gear according to any one of claims 1 to 3, characterised in that each free-wheel (50) of said at least two first free-wheels (51, 52) and at least two second free-wheels (53, 54) comprise an inner ring (55) arranged in an outer ring (56) as well as at least one movable member (57) arranged between the inner ring (55) and the outer ring (56), the inner ring (55) or the outer ring (56) of a free-wheel (56) of a corresponding skid (11, 12) comprising one blocker (58) for each a movable member (57) for securing the inner ring (55) and the outer ring (56) together when the corresponding skid (11, 12) tends to move towards the other skid (12, 11), one of the inner ring (55) and the outer ring (56) being secured to the corresponding roller (30) and the other inner ring (55) or outer ring (56) being connected to a longitudinal bearing part (111, 121) of the corresponding skid (11, 12).

5. Landing gear according to any one of claims 1 to 4, characterised in that the two first rollers (36, 37) are respectively arranged around two first inner rings of the two first free-wheels (51, 52), the two first inner rings being connected to the first skid (11), said two second rollers (41, 42) being respectively arranged around two second inner rings of the two second free-wheels (53, 54), the two second inner rings being connected to the second skid (12).

6. Landing gear according to any one of claims 1 to 5, characterised in that at least one first roller (36, 37) has a first axis of rotation (AXROT1, AXROT11) on itself that is fixed with respect to the first skid (11).

7. Landing gear according to claim 6, characterised in that said first axis of rotation (AXROT1, AXROT11) is parallel to a first longitudinal extension axis (AX1) of a first longitudinal bearing part (111) of the first skid (11), or has an angle different from 0 and 90 degrees with respect to a geometric axis parallel to this first longitudinal extension axis (AX1).

8. Landing gear according to any one of claims 6 to 7, characterised in that said two first rollers (36, 37) have respective first axes of rotation (AXROT1, AXROT11) on themselves that are parallel.

9. Landing gear according to any one of claims 1 to 8, characterised in that at least one second roller (41, 42) has a second axis of rotation (AXROT2, AXROT21) on itself that is fixed with respect to the second skid (12).

10. Landing gear according to claim 9, characterised in that said second axis of rotation (AXROT2, AXROT21) is parallel to a second longitudinal extension axis (AX2) of a second longitudinal bearing part (121) of the second skid (12), or has an angle different from 0 and 90 degrees with respect to a geometric axis parallel to this second longitudinal extension axis (AX2).

11. Landing gear according to any one of claims 9 to 10, characterised in that said two second rollers (41, 42) have respective second axes of rotation (AXROT2) on themselves that are parallel.

12. Landing gear according to any one of claims 6 to 8 and any one of claims 9 to 11, characterised in that said first axis of rotation (AXROT1 , AXROT11) has an angle different from 0 and 90 degrees with respect to a geometric axis parallel to the first longitudinal extension axis (AX1) and said second axis of rotation (AXROT2, AXROT21) has an angle different from 0 and 90 degrees with respect to a geometric axis parallel to the second longitudinal extension axis (AX2), said first axis of rotation (AXROT1, AXROT11) not being parallel to the second axis of rotation (AXROT2, AXROT21).

13. Landing gear according to any one of claims 1 to 5, characterised in that at least one first free-wheel (35) is carried by a first support (69) in pivotal connection with the first skid (11) about a first pivot axis (AXP1) situated in a first transverse plane (P3) orthogonal to a first longitudinal extension axis (AX1) of a first longitudinal bearing part (111) of the first skid (11), at least one second free-wheel (40) being carried by a second support (70) in pivotal connection with the second skid (12) about a second pivot axis (AXP2) situated in a second transverse plane (P5) orthogonal to a second longitudinal extension axis (AX2) of a second longitudinal bearing part (121) of the second skid (12).

14. Landing gear according to claim 13, characterised in that said landing gear (1) comprises at least one actuator (81) connected to at least one of the first support (69) and the second support (70).

15. Landing gear according to any one of claims 1 to 14, characterised in that at least one of the rollers comprises a tyre (31) intended to be in contact with the ground, said tyre (31) being made from a material from the group of elastomers.

16. Landing gear according to any one of claims 1 to 15, characterised in that at least one of the free-wheels (50) is releasable.

17. Aircraft (100), characterised in that said aircraft (100) comprises a landing gear (1) according to any one of claims 1 to 16.

18. Method for limiting the bounce of a landing gear (1) during a landing phase, the landing gear (1) being provided with a first skid (11) and a second skid (12), the method comprising: - during a landing phase, positioning at least two first ground-contact rollers (36, 37) mounted on two respective first free-wheels (51, 52) connected to the first skid (11) in landing positions preventing the first rollers (36, 37) from moving towards the second skid (12), and positioning at least two second ground-contact rollers (41, 42) mounted on two respective second free-wheels connected to the second skid in landing positions preventing the second rollers (41, 42) from moving towards the first skid (11), - during a phase following the landing phase, positioning the at least two first rollers (36, 37) and the at least two second rollers (41, 42) either in respective rolling positions allowing the landing gear (1) to slide on the ground (200) or in respective braking positions, different from the rolling positions, preventing the landing gear (1) from sliding on the ground (200).

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